U.S. Pat. No. 4,634,470, corresponding to Japanese Patent Specification No. 58-244337 as well as publications in "Polymer Journal", Vol. 20, pp. 447-457, 1988, and in "Cellulose Chemistry and Technology", Vol. 24, pp. 23-31, 237-249, 1990, disclose a process of manufacturing cellulose fibers from cellulose pulp by means of the steam explosion method. In this process cellulose is initially treated in an alkaline or acid medium to obtain a polymer with an average degree of polymerization of 200-700, and then this polymer is subjected to a steam explosion treatment at temperatures in the range from 100 to 350.degree. C. under pressures of 1.01 to 2.53 MPa. The treated cellulose dissolves in an aqueous alkaline solution from which fibers can be made by coagulation in an acid coagulation bath. This process does not allow one to obtain modified cellulose with sufficiently high solubility in alkaline solutions. Moreover, the process is technologically and mechanically complicated and energy-consuming.
Polish Patent Specifications No. 167776 and 167519 as well as Finnish patent applications No. 911408 and 910990 specify a method of production of fibers, foils and other products from soluble cellulose obtained on the way of enzymatic treatment by means of cellulolytic enzymes of the cellulase type originated from fungi Aspergillus Niger IBT. The enzymatic treatment of cellulose pulp is carried out at temperatures not lower than 10.degree. C. in a time not shorter than 1 minute at a pH as high as 4-7. This modified cellulose dissolves in aqueous alkali solutions at a temperature from 10.degree. C. to 10.degree. C. in 15 to 2880 minutes. The obtained cellulose solution is filtered and deaerated and then subjected to coagulation in an acid bath.
The enzymatic method causes difficulties in obtaining a high degree of solubility of the modified cellulose and needs the use of expensive enzymes. The preparation of the cellulose spinning solution requires a long stirring time and a low storage temperature while the solution obtained is characterized by poor stability.